Incorrectly installed gear-driven fuel pumps can result in incorrect pump timing relative to the timing of fuel injectors on fuel injected IC engines. For example, if the pump is installed with the pump gear angularly displaced by even one gear tooth relative to design conditions, the control of the pump is compromised. In particular, incorrect pump timing relative to engine timing (i.e. as measured by engine crank angle) can result in unstable fuel rail pressure, and/or limit the maximum flow rate of the pump. Hence, there is a need for apparatus and methods for confirming and/or gear installation. Furthermore, it would be advantageous to provide apparatus and methods for testing for correct pump gear installation in-situ, that is, with the fuel supply system already mounted to the IC engine, such as part of a new engine check out procedure, or during an engine maintenance program. Methods for testing installed fuel supply systems are known, but not for pump gear installation testing. For example, U.S. Pat. No. 5,708,202 to Augustine et al. discloses a method for testing for unacceptable leakage in fuel injection systems installed in IC engines. The method includes measuring pressure in the common fuel rail at two points in time between a fuel injection event and an immediately prior or subsequent pump delivery event. Any difference in measured pressure such as due to system fuel leakage is compared with a predetermined acceptable threshold leakage value. If the pressure difference exceeds the threshold, an “operating error” is indicated. The method also contemplates switching off momentarily at least one of successive fuel injection events and pump delivery events to extend the time period between pressure measurements, to detect small leakage volumes.